1. Field of the Invention
The present invention relates to an air conditioner, and more particularly, to a method for controlling an air conditioner having a multi-compressor.
2. Description of the Conventional Art
Generally, an air conditioner is for cooling indoor warm air or for warming indoor cool air. An air conditioner having two compressors in accordance with the conventional art will be explained with reference to FIG. 1. Said two compressors are selectively operated according to a room cooling load.
FIG. 1 is a schematic view showing a construction of an air conditioner having two compressors in accordance with the conventional art.
As shown, the air conditioner having two compressors comprises: a first compressor 18A and a second compressor 18B selectively operated by a room cooling load for varying a compressing capacity; a condenser 1 for emitting heat of refrigerant compressed by the first and second compressors 18A and 18B; an expansion valve 2 for expanding refrigerant discharged from the condenser 1; and an evaporator 3 for generating cool air by receiving refrigerant expanded by the expansion valve 2. Hereinafter, the air conditioner having said two compressors will be explained in an assumption that the first compressor 18A is a compressor of a small compressing capacity and the second compressor 18B is a compressor of a high compressing capacity.
Suction pipes 9 and 13 respectively connected to the first and second compressors 18A and 18B are connected to each other by hoses 5 and 7 diverged from a suction hose 4 connected to the evaporator 3. Also, discharge pipes 11 and 14 respectively connected to the first compressor 18A and the second compressor 18B are connected to each other by hoses 10 and 16 diverged from a discharge hose 17 connected to the condenser 1.
To each hose 5, 7, 10, and 16, suction valves 6 and 8 and discharge valves 12 and 15 selectively opened closed by a control means such as a handle operation or a microcomputer are respectively connected.
The air conditioner having said two compressors operates the first compressor 18A and the second compressor 18B by a cooling load thus to control a cooling cycle. More concretely speaking, when a room cooling load is small, the air conditioner operates only the first compressor 18A. On the contrary, when the room cooling load is large, the air conditioner operates only the second compressor 18B. When the room cooling load is maximum, the air conditioner operates both said first compressor 18A and said second compressor 18B thus to vary compressing capacities of the compressors.
Recently, an air conditioner provided with four compressors is being used. The air conditioner of four compressors has the same operation as the air conditioner of FIG. 1. The four compressors are designed to have the same compressing capacity or different compressing capacities.
As a method for controlling the air conditioner of four compressors, as shown in FIG. 2, a compressing capacity of the compressor is increased or decreased step by step (10%) according to a cooling load thus to control a room temperature. For example, when a room temperature reaches a temperature lower than a predetermined desired temperature by 0.5° C. under a state that the air conditioner is in a cooling mode, compressing capacities of the compressors are lowered than the previous compressing capacities by one level thus to operate the compressors for a certain time. After the certain time lapses, the room temperature is compared with the desired temperature again. As the result, if the room temperature is not consistent with the desired temperature, the compressing capacities of the compressors are lowered or raised one level by one level thus to operate the compressors.
However, in the method for controlling the air conditioner, the compressing capacity of the compressors has to be lowered or raised one level by one level according to a room cooling load or a heating load, thereby having a slow speed that corresponds to the cooling load or the heating load and increasing an energy loss. For example, if a compressing capacity of the compressors is to be lowered into 50% from 70% under an assumption that a total compressing capacity of the compressors is 100%, the compressing capacity of 70% has to be lowered into 60% first and then the compressing capacity of 60% has to be lowered into 50%. According to this, a speed that corresponds to the cooling load or the heating load is slow and an energy loss is increased.
The air conditioner having the multi-compressor in accordance with the conventional art has been disclosed in U.S. Pat. No. 6,519,957 registered in Feb. 18, 2003.